A Ball State University faculty member helped lead a new study that sheds light on how tooth enamel changed as human diets evolved over millions of years.
Dr. Mackie O’Hara-Ali, an assistant teaching professor in Ball State’s Department of Biology, is a corresponding author of “Enamel nanocrystal misorientation increased with meat-eating and agriculture,” which examines the nanoscale structure of enamel and what it can reveal about human evolution.
Published this month in Nature, one of the world’s leading science journals, the study analyzed enamel nanocrystals in 12 primate teeth spanning nine species and approximately 17.8 million years of evolution. Researchers found that the orientation of enamel nanocrystals changed in connection with diet, including major shifts in the human lineage associated with meat-eating and agriculture.
“Being part of this research team has been an incredible honor,” Dr. O’Hara-Ali said. “This project brought together scientists from anthropology, biology, physics, materials science, and other fields to look at teeth in a new way. I’m deeply grateful to my co-authors for their collaboration and for the care they brought to such a complex study.”
Enamel is the hard outer covering of teeth and the hardest tissue in the human body. While previous research has shown that teeth changed over time in visible ways—such as tooth size, shape, enamel thickness, and wear patterns—this study looked much deeper, examining how enamel adapted at the nanoscale.
Using a newly developed method called Polarization Enabled Large Input of Crystal Angles at the Nanoscale, or PELICAN, the research team found that enamel nanocrystal “misorientation”—small differences in the alignment of adjacent nanocrystals—increased with harder foods in living and fossil primates. In the human lineage, researchers found increases associated with the introduction of meat-eating roughly 2 million to 1.5 million years ago and the transition to agriculture roughly 12,000 years ago.
Those changes may have helped enamel become more resilient as diets changed.
“One of the most exciting takeaways is that enamel preserves a record of how our diets changed—not just at the level we can see with the naked eye, but at the nanoscale,” Dr. O’Hara-Ali said. “These findings help us better understand how teeth responded to major shifts in human behavior and diet, and they may also inform future work on durable, bio-inspired materials.”
The study also found that the more recent Industrial Revolution, which began about 250 years ago, did not produce a significant change in enamel nanocrystal misorientation. Researchers noted that the findings add nanoscale evidence to a broader understanding of how teeth adapted to dietary specialization across human evolution.
The research has also drawn national attention. NPR’s All Things Considered featured the study in a June 5 segment, “What teeth enamel tells us about ancient human diets,” which included comments from Dr. O’Hara-Ali and explored the study’s implications for understanding ancient diets and developing tougher materials.
The open-access article is available through Nature at https://doi.org/10.1038/s41586-026-10583-8.
Dr. O’Hara-Ali joined Ball State’s faculty in August 2025. A biological anthropologist and evolutionary biologist, her research focuses on the biology of human and primate teeth, using them as a window into human development, adaptation, diet, and physiological stress across evolutionary time. Before coming to Ball State, she held research and teaching roles at Purdue University, the University of Kent, and The Ohio State University. She earned her PhD and MA in physical and biological anthropology from The Ohio State University and her BA in anthropology from the University of Arkansas at Little Rock.